Simple flight vehicles, such as gliding or guided bombs or defence rockets can be directed to their targets with the aid of a laser guiding system. An operator ‘lights’ a target with suitable radiation and the tracking device detects the radiation spot on the target and guides the flight vehicle towards the target. In order to detect the radiation on the target, a target guiding device can comprise a detector for example, a quadrant detector, where the radiation is incident on four detector cells. The flight vehicle is directed toward the target such that the same parts of the radiation spot are imaged on the four detector cells. However, as such a narrow non-detecting area is arranged between the detector cells, the target tracking can result in errors.
Alternative detectors have been proposed. For example GB-A-2415310 discloses a target tracking device utilising a Position Sensitive Detector (PSD) in an integrating pre-amplifier system. In such a configuration, pulses output by the PSD in response to the incident radiation are integrated and, after some signal processing by control electronics, a control signal is output, capable of directing the flight vehicle toward the target.
It is a disadvantage of a device incorporating a PSD that integrating pulses can result in energy loss, particularly in the energy not immediately detected as the pulse time is short but the response time of the PSD is relatively long.